Which of the following layers of the GI tract contains skeletal muscle?

• A. Submucosa
• B. Muscularis externa of the upper esophagus
• C. Mucosa
• D. Serosa

Answer: (B)

Verified step by step guidance

1. Understand the structure of the gastrointestinal (GI) tract, which consists of four main layers: mucosa, submucosa, muscularis externa, and serosa.
2. Recognize that the muscularis externa is primarily composed of smooth muscle throughout most of the GI tract, but in specific regions, such as the upper esophagus, it contains skeletal muscle.
3. Recall that skeletal muscle is under voluntary control, which is necessary for the initial stages of swallowing in the upper esophagus.
4. Eliminate the other options: the mucosa is the innermost layer responsible for secretion and absorption, the submucosa contains connective tissue, blood vessels, and nerves, and the serosa is the outermost protective layer.
5. Conclude that the correct answer is the muscularis externa of the upper esophagus, as it is the only layer in the GI tract that contains skeletal muscle in this specific region.